1. Field of the Invention
The present invention relates generally to the field of microprocessor systems, and more particularly, to a reset circuit for a microprocessor system.
2. Discussion of Related Art
All computer systems have some type of reset circuit. The purpose of the reset circuit is to initialize a CPU's internal storage locations (e.g., the general state of the machine). Typically during a reset operation, all registers are set to zero, the interrupt system is disabled, the input/output interface is initialized, and the program counter is set to some initial value. The terms reset, power up (from a cold or warm start), and boot are used interchangeably throughout this document. Typically, the reset signal is generated external to the CPU.
It is extremely important that the system designer design the system to guarantee that the CPU starts last after the reset pin becomes inactive. Once the reset funtions of the CPU begin, the CPU is initialized to some predetermined state and a defined sequence of events begins. It is essential that all the chips peripheral to the CPU initialize before the CPU is allowed to access their memory locations; otherwise, the CPU will be accessing invalid data.